Vacuum cleaner and method of controlling a motor for a brush of the vacuum cleaner

ABSTRACT

A vacuum cleaner that includes a surface cleaning head including a dirty air inlet, a brush supported by the surface cleaning head, a motor coupled to and operable to cause movement of the brush, a sensor to sense a voltage associated with a current of the motor, and a controller configured to control an amount of current provided to the motor in response to the sensed voltage. The controller is configured to control a first pulse width modulated (PWM) duty cycle provided to the motor when the sensed voltage is less than a reference voltage, control a second PWM duty cycle provided to the motor when the sensed voltage is greater than the reference voltage, the second PWM duty cycle being less than the first PWM duty cycle, and turn off the motor when the sensed voltage increases to a voltage associated with an overload current of the motor.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/878,501, filed Jan. 24, 2018, which claims the benefit of ChinesePatent Application No. 201710997069.XA, filed Oct. 20, 2017, and theentire contents of each are hereby incorporated by reference.

BACKGROUND

The invention relates to a vacuum cleaner including a surface cleaninghead having a brush and motor for operating the brush.

Upright vacuum cleaners are typically used to clean floor surfaces, suchas carpeting. Sometimes the carpeting can have a long pile height orother attribute providing a significant resistance to the brush of thevacuum cleaner.

SUMMARY

A first aspect of the disclosure provides a vacuum cleaner that includesa surface cleaning head including a dirty air inlet, a brush supportedby the surface cleaning head, a motor coupled to and operable to causemovement of the brush, a sensor to sense a voltage associated with acurrent of the motor, and a controller configured to control an amountof current provided to the motor in response to the sensed voltage. Thecontroller is configured to control a first pulse width modulated (PWM)duty cycle provided to the motor when the sensed voltage is less than areference voltage, control a second PWM duty cycle provided to the motorwhen the sensed voltage is greater than the reference voltage, thesecond PWM duty cycle being less than the first PWM duty cycle, and turnoff the motor when the sensed voltage increases to a voltage associatedwith an overload current of the motor.

Another aspect of the disclosure provides a method of controlling amotor for a brush of a vacuum cleaner. The method includes sensing avoltage associated with a current of the motor, controlling a firstpulse width modulated (PWM) duty cycle provided to the motor when thesensed voltage is less than a reference voltage, and controlling asecond PWM duty cycle provided to the motor when the sensed voltage isgreater than the reference voltage, the second PWM duty cycle being lessthan the first PWM duty cycle. The method further includes turning offthe motor when the sensed voltage increases to a voltage associated withan overload current of the motor.

Other aspects of the invention will become apparent by consideration ofthe detailed description and accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a vacuum cleaner according to anembodiment of the invention.

FIG. 2 is a sectional view of a portion of the vacuum cleaner of FIG. 1.

FIG. 3 is a block diagram of a portion of the control circuit for thevacuum cleaner of FIG. 1

FIG. 4 is a block diagram of a portion of the firmware used to controlthe brush motor of the control circuit of FIG. 3.

DETAILED DESCRIPTION

Before any embodiments of the invention are explained in detail, it isto be understood that the invention is not limited in its application tothe details of construction and the arrangement of components set forthin the following description or illustrated in the following drawings.The invention is capable of other embodiments and of being practiced orof being carried out in various ways.

FIG. 1 illustrates an exemplary vacuum cleaner 10. The vacuum cleaner 10includes a surface cleaning head 15, a pivot assembly 20, and a canisterassembly 25. The vacuum cleaner 10 further includes an upright handle30. The vacuum cleaner 10 shown in FIG. 1 is typically referred to as anupright vacuum cleaner. However, the invention is not limited to uprightvacuum cleaners, i.e., can be used in other vacuum types for examplecanister vacuums, stick vacuums, and robot vacuums, and the arrangementof the upright vacuum cleaner can vary from the vacuum cleaner 10 shownin FIG. 1.

In the illustrated embodiment of FIG. 1, the surface cleaning head 15 ismovable along a surface 35 to be cleaned, such as a carpeted floor. Theupright handle 30 allows a user to move the surface cleaning head 15along the surface 35. The upright handle 30 is also movable relative tothe surface cleaning head 15 between an upright position (FIG. 1) and aninclined position.

The surface cleaning head 15 includes a dirty air inlet 40 (shown inFIG. 2). The surface cleaning head further includes a brushroll (alsoreferred to as a brush) 45 for agitating the surface 35 being cleaned.The brush 45 is driven by a brush motor 50 (shown in FIG. 3).

The vacuum cleaner 10 includes other electrical components besides thebrush motor 50 that are part of an appliance control circuit 55. Withreference to FIG. 3, the control circuit 55 further includes anappliance controller 60, a suction motor 65, a user interface, andsensors.

The appliance controller 60 includes combinations of software andhardware that are operable to, among other things, control the operationof the vacuum 10, receive input from the sensors, receive input orprovide output with the user interface, and control the motors 50 and65.

In one construction, the appliance controller 60 includes a printedcircuit board (“PCB”) that is populated with a plurality of electricaland electronic components that provide, power, operational control, andprotection to the vacuum 10. In some constructions, the PCB includes,for example, a processing unit 70 (e.g., a microprocessor, amicrocontroller, or another suitable programmable device) and a memory75. The memory 75 includes, for example, a read-only memory (“ROM”), arandom access memory (“RAM”), an electrically erasable programmableread-only memory (“EEPROM”), a flash memory, or another suitablemagnetic, optical, physical, or electronic memory device. The processingunit 70 is connected to the memory 75 and executes instructions (e.g.,software) that is capable of being stored in the RAM (e.g., duringexecution), the ROM (e.g., on a generally permanent basis), or anothernon-transitory computer readable medium such as another memory or adisc. Additionally or alternatively, the memory 75 is included in theprocessing unit 70 (e.g., as part of a microcontroller).

Software included in this implementation of the vacuum cleaner 10 isstored in the memory 75 of the appliance controller 60. The softwareincludes, for example, firmware, program data, one or more programmodules, and other executable instructions. The appliance controller 60is configured to retrieve from memory and execute, among other things,instructions related to the control processes and methods describedherein.

The PCB also includes, among other things, a plurality of additionalpassive and active components such as resistors, capacitors, inductors,integrated circuits, and amplifiers. These components are arranged andconnected to provide a plurality of electrical functions to the PCBincluding, among other things, signal conditioning or voltageregulation. For descriptive purposes, the PCB and the electricalcomponents populated on the PCB are collectively referred to as theappliance controller 60. It should also be noted that the current sensor(discussed below), for example can be mounted on the PCB and alsoconsidered part of the appliance controller 60. However, for ease ofdescription, the current sensor will be described separately.

The user interface is included to control the vacuum cleaner 10. Theuser interface can include a combination of digital and analog inputdevices to control the vacuum cleaner 10. For example, the userinterface can include a display 80 and a switch 85, or the like. Thedisplay 80 can be as simple as LEDs indicating operation of the vacuumcleaner 10, and the switch 85 can be used for activating/deactivatingthe vacuum cleaner 10. The display 80 can be mounted on a PCB with otheradditional passive and active components necessary for controlling thedisplay, similar to what was discussed for the appliance controller 60,or can be mounted on the PCB for the appliance controller 60.

The appliance controller 60 operates the brushroll motor 50 and thesuction motor 65, the operation of which may be based on a floor type.For example, the appliance controller 60 may operate the suction motor65 at a lower power on a hard floor surface to conserve energy or ahigher power on a hard floor surface to increase debris pick-up. In someembodiments, the brushroll motor 50 may be operated at a lower power oncertain height carpets to reduce the action of the brushroll 45 to thecarpet and the force applied from the carpet to the brushroll, or carpetload, so that the vacuum cleaner 10 is less likely to stall, forexample.

The current sensor 90 (also sometimes referred to as the brushrollsensor) refers to a sensor that senses an electrical parameter relateddirectly or indirectly to an aspect of carpet load restricting thebrush. An exemplary parameter may be the amount of current to or throughthe brushroll motor 50. The brushroll sensor can be a tachometer forsensing a revolutions per minute (RPM) value of the brushroll 45, atachometer for sensing an RPM value of the brushroll motor 50, anelectrical sensor (e.g., the current sensor) for sensing an electricalparameter (e.g., current or voltage) of the brushroll motor 50, a torquesensor for sensing a torque parameter of the brushroll motor 50, etc. Itis envisioned that the number of sensors can be greater than the singlesensor shown.

With reference to the implementation of FIG. 3, the vacuum cleaner 10includes a current sensor 90 and an appliance controller 60 incommunication with the current sensor 90. The current sensor 90 isconfigured to sense a parameter indicative of the current draw of thebrushroll motor 50. The appliance controller 60 receives a signal fromthe current sensor 90 and compares the signal with a correspondingpredetermined threshold. In some implementations, the appliancecontroller 60 includes an overload protection that will stop thebrushroll motor 50 and/or vacuum cleaner operation after sensing aparameter related to an overload current (e.g., 2.3 amps in one specificexample). In order to preserve the life of the brushroll motor 50 acurrent stall indication may be provided to the user before the overloadcurrent, or failure threshold is met. However, a load of this magnitudeis possible during normal use on high pile carpet height, for example.In order to prevent the current stall from occurring, a mechanical airbleed may be provided in the suction flow path of the vacuum cleaner 10to provide inflow of air to the vacuum through the air bleed. The useris instructed to open the mechanical bleed if they are experiencing abrushroll stall event during normal use because the inflow of air to thevacuum reduces the amount of suction at the nozzle, reducing the nozzleengagement to the carpet caused by suction. Opening of the mechanicalbleed reduces both the carpet load on the brushroll 45 and also thecleaning efficiency of the vacuum cleaner 10 itself.

An alternative, or even additive, approach is to monitor the currentbeing fed through the brushroll motor 50 and to automatically adjust viapulse width modulation (PWM) the voltage input to the brushroll motor50. As a result of decreasing the voltage to the brushroll motor 50, thecurrent consumption of the brushroll motor 50 will also decrease as wellas the speed of the brushroll 45 itself. As a result, the brushrollmotor 50 can be automatically protected without user intervention.

In FIG. 3, a control signal 95 is a PWM signal from the controller 60.When the PWM signal is high, current flows through the switch 100 to thebrushroll motor 50. When the PWM signal is low, current is restricted bythe switch 100. The actual average motor input voltage can be varied byadjusting the PWM signal from a maximum to a minimum duty cycle.

The current through the brushroll 50 is monitored with the currentsensor 90. In one embodiment, a voltage indicative of the brushrollcurrent is acquired from a secondary side of a transformer in a currentpath from the switch 85 to the brushroll motor 50. In an alternativeembodiment, a voltage indicative of the brushroll current is acquiredfrom a resistor network in a current path between the switch 85 and thebrushroll motor 50. Firmware of the appliance controller 60 usesinformation gained from the current sensor signal to make adjustments tothe control signal 95 to decrease the voltage at the motor as a resultof increased current due to loading as a result of high pile carpet.

An exemplary firmware logic is shown in FIG. 4. A reference voltage 105is set in the firmware. The reference voltage is less than the voltageassociated with the overload current and selected to extend thebrushroll motor run time in desired user conditions. The referencevoltage may be a voltage providing a corresponding current that is afunction of the overload current, such as 80% or 85% or 90% or otherfunction of the overload current of the brushroll motor. Alternativelyor additionally, the reference voltage is empirically determined toextend the brushroll motor run time a desired amount in the usercondition. In one specific example, a reference voltage associated with2.1 Amps is the maximum voltage that an implementation allows the PWMsignal to operate with 100 percent duty.

The vacuum cleaner 10 is turned on by the user with switch 85 andinformation is acquired via the current sensor 90. The firmwaredetermines a difference between the current signal and the set pointreference (at 110). The firmware uses a filter, such as a proportional,integral, and derivative (PID) filter 115, to filter the peaks andvalleys out of the signal. If the current measurement is smaller thanthe reference voltage (at 120), the PWM duty cycle is increased to a PWMvalue. In some implementations, the PWM value is set to maximum voltage(e.g., 100 percent duty cycle). In other implementations, the PWM valueis incremented by a value amount (e.g., 10 percent) until the maximumduty cycle is obtained. The PWM duty cycle typically remains at themaximum duty cycle until the voltage at the brushroll motor is equal toor larger than the reference voltage.

If the voltage associated with the brushroll current measurement islarger than the reference voltage, the PWM value is decreased to extendthe brushroll motor run time before reaching the overload current. Insome implementations, the PWM value is decremented by a value amount(e.g., 10 percent) until a minimum duty cycle is obtained. For example,the minimum duty cycle value may be 50 percent. In an alternativeimplementation, the PWM value is decremented as a function of thereference voltage until the minimum duty cycle is obtained. In yetanother implementation, the duty cycle is set to a first PWM duty cyclewhen the voltage is smaller than the reference voltage and a second,non-zero, PWM duty cycle when the voltage is larger than the referencevoltage. For example, the duty cycle may be 100% when the voltageassociated with the brushroll current measurement is below the referencevoltage and the duty cycle may be 50% when the voltage is above thereference voltage. If the firmware wants to reduce the PWM value to beless than the minimum duty cycle value, then a current stall indicationmay be displayed to the user. The brushroll motor continues to operateat the reduced PWM duty cycle value until the current sensor signal ofthe brushroll motor either increases to the predetermined voltageassociated with the overload current or decreases to below the referencevoltage. When the brushroll motor current reaches the overload current,the controller turns off the brushroll motor. When the voltage of thecurrent sensor drops below the reference voltage, the controllerincreases the PWM duty cycle value. In one embodiment, when the measuredvoltage drops below the reference voltage, the controller determineswhether the PWM duty cycle value is less than an upper limit. The upperduty cycle limit may be 100%, or may be a lower limit such as 95% or 90%or any other desired predetermined limit. If the PWM duty cycle value isless than an upper limit and the measured voltage is less than thereference voltage, the controller increases the PWM duty cycle value.The controller may increase the PWM duty cycle to the upper limit or mayincrease the PWM duty cycle a predetermined amount.

Accordingly, the invention provides a new and useful vacuum cleaner andmethod of controlling a motor for a brush of the vacuum cleaner. Variousfeatures and advantages of the invention are set forth in the followingclaims.

1. A vacuum cleaner comprising: a surface cleaning head including a dirty air inlet; a brush supported by the surface cleaning head; a motor coupled to and operable to cause movement of the brush; a sensor to sense a voltage associated with a current of the motor; and a controller configured to control an amount of current provided to the motor in response to the sensed voltage, including the controller configured to: control a first pulse width modulated (PWM) duty cycle provided to the motor when the sensed voltage is less than a reference voltage, control a second PWM duty cycle provided to the motor when the sensed voltage is greater than the reference voltage, the second PWM duty cycle being less than the first PWM duty cycle, and turn off the motor when the sensed voltage increases to a voltage associated with an overload current of the motor.
 2. The vacuum cleaner of claim 1, wherein the controller further includes a processing unit and non-transitory memory with instructions executable by the processing unit, the instructions when executed by the processing unit include the processing unit determining whether the sensed voltage is less than, greater than, or equal to the reference voltage, and generating a signal for controlling the motor.
 3. The vacuum cleaner of claim 2, wherein the processing unit generating the signal includes decreasing the first PWM duty cycle to the second PWM duty cycle when the sensed voltage is greater than the reference voltage.
 4. The vacuum cleaner of claim 2, wherein the processing unit generating the signal includes decreasing the first PWM duty cycle to the second PWM duty cycle when the sensed voltage is equal to the reference voltage.
 5. The vacuum cleaner of claim 2, wherein the processing unit generating the signal includes increasing the second PWM duty cycle to the first PWM duty cycle when the sensed voltage is less than the reference voltage.
 6. The vacuum cleaner of claim 1, wherein the first PWM duty cycle is a maximum duty cycle and the second PWM duty cycle is a minimum duty cycle, and when the sensed voltage is greater than the reference voltage, the maximum duty cycle is decremented by a percentage value until the minimum duty cycle is obtained.
 7. The vacuum cleaner of claim 6 further comprising a display configured to provide a current stall indication to a user regarding a reduction of the second PWM duty cycle to below the minimum duty cycle, the current stall indication provided after sensing a parameter related to the overload current.
 8. The vacuum cleaner of claim 7, wherein the current stall indication includes instructions for the user to open a mechanical air bleed.
 9. The vacuum cleaner of claim 1, wherein the first PWM duty cycle is a 100 percent duty cycle.
 10. The vacuum cleaner of claim 1, wherein the second PWM duty cycle is a 50 percent duty cycle.
 11. A method of controlling a motor for a brush of a vacuum cleaner, the method comprising: sensing a voltage associated with a current of the motor; controlling a first pulse width modulated (PWM) duty cycle provided to the motor when the sensed voltage is less than a reference voltage, controlling a second PWM duty cycle provided to the motor when the sensed voltage is greater than the reference voltage, the second PWM duty cycle being less than the first PWM duty cycle, and turning off the motor when the sensed voltage increases to a voltage associated with an overload current of the motor.
 12. The method of claim 11, further comprising: determining, by a controller including a processing unit and non-transitory memory with instructions executable by the processing unit, whether the sensed voltage is less than, greater than, or equal to the reference voltage; and generating, by the controller, a signal for controlling the motor.
 13. The method of claim 12, wherein generating the signal includes decreasing, by the controller, the first PWM duty cycle to the second PWM duty cycle when the sensed voltage is greater than the reference voltage.
 14. The method of claim 12, wherein generating the signal includes decreasing, by the controller, the first PWM duty cycle to the second PWM duty cycle when the sensed voltage is equal to the reference voltage.
 15. The method of claim 12, wherein generating the signal includes increasing, by the controller, the second PWM duty cycle to the first PWM duty cycle when the sensed voltage is less than the reference voltage.
 16. The method of claim 11, wherein the first PWM duty cycle is a maximum duty cycle and the second PWM duty cycle is a minimum duty cycle, and wherein the method further comprises decrementing the maximum duty cycle by a percentage value until the minimum duty cycle is obtained when the sensed voltage is greater than the reference voltage.
 17. The method of claim 16, further comprising displaying, on a display of the vacuum cleaner, a current stall indication to a user regarding a reduction of the second PWM duty cycle to below the minimum duty cycle after sensing a parameter related to the overload current.
 18. The method of claim 17, wherein displaying the current stall indication includes instructing the user to open a mechanical air bleed.
 19. The method of claim 11, wherein the first PWM duty cycle is a 100 percent duty cycle.
 20. The method of claim 11, wherein the second PWM duty cycle is a 50 percent duty cycle. 